1. Field of the Invention
The present invention relates to a developing device, particularly, a developing device which supplies developer to an electrostatic latent image bearing body of an image forming apparatus.
2. Description of the Related Art
In a developing device which supplies toner particles to an electrostatic latent image bearing body of an image forming apparatus, an opening is provided in a position opposite to the electrostatic latent image bearing body. From this opening, a developing roller is exposed. In this type of image forming apparatus, a regulating member is provided in a state of facing the developing roller, which regulates the thickness of a toner layer on the developing roller. In such a developing device, toner particles are supplied onto the developing roller. As the developing roller rotates, the developing roller and the regulating member can regulate the toner-layer thickness on the developing roller. Herein, the positional relation between the developing roller and the regulating member determines the toner layer thickness. This requires precise arrangement of the developing roller and the regulating member with respect to each other.
Therefore, a developing device has been worked out which is capable of positioning such a developing roller and a regulating member with precision (refer to Japanese Patent Laid-Open Publication No. 5-88527). In this developing device, in order to accurately arrange the developing roller and the regulating member, the developing roller and a plate member are attached to an attachment member to be attached to a developing unit. To this plate member, the regulating member is fixedly attached.
However, in the developing device according to this patent document, because the regulating member is fixedly attached to the plate member, the tolerance which must be considered for production between the regulating member and the developing roller has three tolerances, that is, a tolerance between the regulating member and the plate member, a tolerance between the plate member and the attachment member, and a tolerance between the developing roller and the attachment member. Hence, deviations in the three tolerances are accumulated, thus making it difficult to precisely arrange the regulating member with respect to the developing roller. This is likely to hinder the regulating member from running parallel to the developing roller, or to cause their respective axes to shift from each other (i.e., twisted relation) even if they are parallel. In such a case, a uniform toner layer cannot be formed on the developing roller.